makes the header names configurable

Author: ChristianPavilonis

crates/common/build.rs

@@ -14,6 +14,7 @@ const TRUSTED_SERVER_OUTPUT_CONFIG_PATH: &str = "../../target/trusted-server-out
 
 fn main() {
     merge_toml();
+    generate_header_constants();
     rerun_if_changed();
 }
 
@@ -57,6 +58,37 @@ fn merge_toml() {
     fs::write(dest_path, merged_toml).unwrap_or_else(|_| panic!("Failed to write {:?}", dest_path));
 }
 
+fn generate_header_constants() {
+    // Read and parse the config
+    let init_config_path = Path::new(TRUSTED_SERVER_INIT_CONFIG_PATH);
+    let toml_content = fs::read_to_string(init_config_path)
+        .unwrap_or_else(|_| panic!("Failed to read {:?}", init_config_path));
+
+    let settings = settings::Settings::from_toml(&toml_content)
+        .expect("Failed to parse settings at build time");
+
+    // Generate the header name based on psid
+    let psid = &settings.publisher.psid;
+    let header_name = format!("x-{}-ts", psid);
+
+    // Generate Rust code for the constant
+    let generated_code = format!(
+        r#"// This file is auto-generated by build.rs - DO NOT EDIT
+
+pub const HEADER_SYNTHETIC_TRUSTED_SERVER: HeaderName = HeaderName::from_static("{}");
+"#,
+        header_name
+    );
+
+    // Write to OUT_DIR
+    let out_dir = std::env::var("OUT_DIR").expect("OUT_DIR not set");
+    let dest_path = Path::new(&out_dir).join("generated_header_constants.rs");
+    fs::write(&dest_path, generated_code)
+        .unwrap_or_else(|_| panic!("Failed to write {:?}", dest_path));
+
+    println!("cargo:warning=Generated header constant: {}", header_name);
+}
+
 fn collect_env_vars(value: &Value, env_vars: &mut HashSet<String>, path: Vec<String>) {
     if let Value::Object(map) = value {
         for (key, val) in map {

crates/common/src/constants.rs

@@ -3,8 +3,9 @@ use http::header::HeaderName;
 pub const HEADER_SYNTHETIC_FRESH: HeaderName = HeaderName::from_static("x-synthetic-fresh");
 pub const HEADER_SYNTHETIC_PUB_USER_ID: HeaderName = HeaderName::from_static("x-pub-user-id");
 pub const HEADER_X_PUB_USER_ID: HeaderName = HeaderName::from_static("x-pub-user-id");
-pub const HEADER_SYNTHETIC_TRUSTED_SERVER: HeaderName =
-    HeaderName::from_static("x-psid-ts");
+
+// Generated at build time from publisher.id_prefix in trusted-server.toml
+include!(concat!(env!("OUT_DIR"), "/generated_header_constants.rs"));
 pub const HEADER_X_CONSENT_ADVERTISING: HeaderName =
     HeaderName::from_static("x-consent-advertising");
 pub const HEADER_X_FORWARDED_FOR: HeaderName = HeaderName::from_static("x-forwarded-for");

crates/common/src/settings.rs

@@ -23,6 +23,14 @@ pub struct Publisher {
     /// Secret used to encrypt/decrypt proxied URLs in `/first-party/proxy`.
     /// Keep this secret stable to allow existing links to decode.
     pub proxy_secret: String,
+    /// Prefix for the publisher-specific ID header (x-{psid}-ts).
+    /// Defaults to "psid" if not specified.
+    #[serde(default = "default_psid")]
+    pub psid: String,
+}
+
+fn default_psid() -> String {
+    "psid".to_string()
 }
 
 impl Publisher {
@@ -568,6 +576,7 @@ mod tests {
             cookie_domain: ".example.com".to_string(),
             origin_url: "https://origin.example.com:8080".to_string(),
             proxy_secret: "test-secret".to_string(),
+            psid: "psid".to_string(),
         };
         assert_eq!(publisher.origin_host(), "origin.example.com:8080");
 
@@ -577,6 +586,7 @@ mod tests {
             cookie_domain: ".example.com".to_string(),
             origin_url: "https://origin.example.com".to_string(),
             proxy_secret: "test-secret".to_string(),
+            psid: "psid".to_string(),
         };
         assert_eq!(publisher.origin_host(), "origin.example.com");
 
@@ -586,6 +596,7 @@ mod tests {
             cookie_domain: ".example.com".to_string(),
             origin_url: "http://localhost:9090".to_string(),
             proxy_secret: "test-secret".to_string(),
+            psid: "psid".to_string(),
         };
         assert_eq!(publisher.origin_host(), "localhost:9090");
 
@@ -595,6 +606,7 @@ mod tests {
             cookie_domain: ".example.com".to_string(),
             origin_url: "localhost:9090".to_string(),
             proxy_secret: "test-secret".to_string(),
+            psid: "psid".to_string(),
         };
         assert_eq!(publisher.origin_host(), "localhost:9090");
 
@@ -604,6 +616,7 @@ mod tests {
             cookie_domain: ".example.com".to_string(),
             origin_url: "http://192.168.1.1:8080".to_string(),
             proxy_secret: "test-secret".to_string(),
+            psid: "psid".to_string(),
         };
         assert_eq!(publisher.origin_host(), "192.168.1.1:8080");
 
@@ -613,6 +626,7 @@ mod tests {
             cookie_domain: ".example.com".to_string(),
             origin_url: "http://[::1]:8080".to_string(),
             proxy_secret: "test-secret".to_string(),
+            psid: "psid".to_string(),
         };
         assert_eq!(publisher.origin_host(), "[::1]:8080");
     }

trusted-server.toml

@@ -8,6 +8,7 @@ domain = "test-publisher.com"
 cookie_domain = ".test-publisher.com"
 origin_url = "https://origin.test-publisher.com"
 proxy_secret = "change-me-proxy-secret"
+psid = "psid"
 
 [prebid]
 server_url = "http://68.183.113.79:8000"